docstr: Export the model to ONNX format.
  
  Args:
      dirname(str): The directory to save the onnx model.
      input_shape_dict: dictionary ``{ input_name: input_value }, eg. {'x': [-1, 3, -1, -1]}``
      opset_version(int): operator set
docstr_tok: ["Export","the","model","to","ONNX","format",".","Args",":","dirname","(","str",")",":","The","directory","to","save","the","onnx","model",".","input_shape_dict",":","dictionary","``","{","input_name",":","input_value","}",",","eg",".","{","'","x","'",":","[","-1",",","3",",","-1",",","-1","]","}","``","opset_version","(","int",")",":","operator","set"]
code: def export_onnx_model(
      self, dirname: str, input_shape_dict=None, opset_version=10
  ):
      """
      Export the model to ONNX format.
  
      Args:
          dirname(str): The directory to save the onnx model.
          input_shape_dict: dictionary ``{ input_name: input_value }, eg. {'x': [-1, 3, -1, -1]}``
          opset_version(int): operator set
      """
      self.model.export_onnx_model(
          dirname=dirname,
          input_shape_dict=input_shape_dict,
          opset_version=opset_version,
      )
  
file_path: PaddleHub/modules/image/text_recognition/german_ocr_db_crnn_mobile/module.py
imports: import paddlehub
  from paddleocr.ppocr.utils.logging import get_logger
  from paddleocr.tools.infer.utility import base64_to_cv2
  from paddlehub.module.module import moduleinfo, runnable, serving
label_desc: Use image node_id 5 for calling the GermanOCRDBCRNNMobile obj's underlying member method code with example usage: obj.export_onnx_model(dirname, input_shape_dict, opset_version) without return types